Binding of HTm4 to Cyclin-dependent Kinase (Cdk)-associated Phosphatase (KAP)·Cdk2·Cyclin A Complex Enhances the Phosphatase Activity of KAP, Dissociates Cyclin A, and Facilitates KAP Dephosphorylation of Cdk2

Chinami, Masanobu; Yano, Yoshihiko; Yang, Xing; Salahuddin, Saira; Moriyama, Kosei; Shiroishi, Mitsunori; Turner, Helen; Shirakawa, Taro; Adra, Chaker N.

doi:10.1074/jbc.m413437200

Cited by 30 publications

(34 citation statements)

References 23 publications

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“…This can be attributed primarily to GPR84 knockdown-mediated upregulation of Ms4a3, which induces G1-phase cell-cycle arrest in HSCs and primary AML blasts. 31,32,55 Collectively, our study therefore demonstrates a multifaceted regulatory function of GPR84 in leukemia formation and shows a strong dependence of MLL leukemic cells on GPR84 for growth and survival in vitro and in vivo. The dramatic effect of GPR84 on stem cell-derived MLL leukemogenesis suggests that GPR84 is a direct target of MLL-AF9-dependent transformation in vivo and highlights the importance of this signaling molecule in this disease.…”

Section: Discussionmentioning

confidence: 52%

“…by guest www.bloodjournal.org From a substantial reduction in the expression of a G1-S phase cell-cycle inhibitor, Ms4a3. 31,32 This could thus explain the result shown in Figure 2D that GPR84 knockdown induced G1 arrest in KLSMLL pre-LSCs, likely through reactivation of Ms4a3. We also noted a pronounced increase in both mRNA and protein levels of b-catenin transcriptional cofactors including Tcf7l2 and c-Fos in GPR84-overexpressing KLSA9M pre-LSCs ( Figure 6B,G), [33][34][35][36][37] indicating GPR84-mediated potentiation of Wnt/b-catenin signaling.…”

Section: Blood 20 November 2014 X Volume 124 Number 22 the Importanmentioning

confidence: 81%

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GPR84 sustains aberrant β-catenin signaling in leukemic stem cells for maintenance of MLL leukemogenesis

Dietrich

Yang

Leung

et al. 2014

Blood

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Key Points• GPR84 simultaneously augments b-catenin signaling and an oncogenic transcription program essential for establishment of MLL.• Our study demonstrates a strong dependence of hematopoietic stem cell-derived MLL leukemic cells on GPR84 for disease maintenance in vivo.b-catenin is required for establishment of leukemic stem cells (LSCs) in acute myeloid leukemia (AML). Targeted inhibition of b-catenin signaling has been hampered by the lack of pathway components amenable to pharmacologic manipulation. Here we identified a novel b-catenin regulator, GPR84, a member of the G protein-coupled receptor family that represents a highly tractable class of drug targets. High GPR84 expression levels were confirmed in human and mouse AML LSCs compared with hematopoietic stem cells (HSCs). Suppression of GPR84 significantly inhibited cell growth by inducing G1-phase cell-cycle arrest in pre-LSCs, reduced LSC frequency, and impaired reconstitution of stem cell-derived mixed-lineage leukemia (MLL) AML, which represents an aggressive and drug-resistant subtype of AML. The GPR84-deficient phenotype in established AML could be rescued by expression of constitutively active b-catenin. Furthermore, GPR84 conferred a growth advantage to Hoxa9/Meis1a-transduced stem cells. Microarray analysis demonstrated that GPR84 significantly upregulated a small set of MLL-fusion targets and b-catenin coeffectors, and downregulated a hematopoietic cell-cycle inhibitor. Altogether, our data reveal a previously unrecognized role of GPR84 in maintaining fully developed AML by sustaining aberrant b-catenin signaling in LSCs, and suggest that targeting the oncogenic GPR84/b-catenin signaling axis may represent a novel therapeutic strategy for AML. (Blood. 2014;124(22):3284-3294) IntroductionThe ability for self-renewal, migration/invasion, and drug resistance are fundamental properties of malignant stem cells that drive both disease progression and relapse. Identification of pathways and their molecular components essential for the regulation of abnormally acquired stem cell-like properties is a prerequisite for understanding the underlying mechanisms of oncogenesis and designing effective anticancer therapeutic strategies. We and others have previously shown that mixed-lineage leukemia (MLL) fusion proteins can aberrantly activate Wnt/b-catenin signaling in hematopoietic stem cells (HSCs) or more differentiated granulocyte-macrophage progenitors (GMPs) for establishment of leukemic stem cells (LSCs) in acute myeloid leukemia subtype M5 (AML-M5) 1,2 ; however, the mechanisms involved remain obscure. It has also been noted that activation of b-catenin is observed in tumors without clear mutations in major components of this pathway or an increase in Wnt signaling.3 This suggests that other developmental signaling pathways may be capable of inducing activation or downstream signaling of b-catenin.G protein-coupled receptors (GPCRs), the largest family of cell-surface molecules with key roles in transmitting signals to downstream effectors, ...

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Section: Discussionmentioning

confidence: 52%

Section: Blood 20 November 2014 X Volume 124 Number 22 the Importanmentioning

confidence: 81%

GPR84 sustains aberrant β-catenin signaling in leukemic stem cells for maintenance of MLL leukemogenesis

Dietrich

Yang

Leung

et al. 2014

Blood

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“…The increase in Cdk2 phosphorylation was consistent with the observed dominant negative effect of the d splice variant on proliferation, whereas the absence of a change in cdc2 protein levels was consistent with the observation that the d variant had no effect on cdc2-dependent cell migration. One possible explanation for this result is that the truncated KAP variant d interacts with other KAP-binding proteins (e.g., Htm4) to selectively inhibit KAP-mediated Cdk2-dephosphorylation, thereby promoting proliferation but not migration (8).…”

Section: à6mentioning

confidence: 99%

“…Recent evidence suggests that another protein, Htm4, participates in a protein complex with KAP and Cdk2 to promote KAP phosphatase activity and inhibit cell cycle (7,8). Interestingly, KAP also binds to two other cell cycle regulators, cdc2 and Cdk3 (4,5).…”

Section: Introductionmentioning

confidence: 99%

Aberrant Splicing of Cyclin-Dependent Kinase–Associated Protein Phosphatase KAP Increases Proliferation and Migration in Glioblastoma

Jiang

Schoch

et al. 2007

Cancer Research

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The cyclin-dependent kinase (Cdk)-associated protein phosphatase KAP is a dual-specificity phosphatase of which the only known function is to dephosphorylate Cdk2 and inhibit cell cycle progression. Paradoxically, we find increased KAP mRNA expression in malignant astrocytomas, which correlates with increasing histologic grade and decreased patient survival. We have resolved this apparent paradox with the discovery of aberrant KAP splicing in malignant astrocytomas that leads to increased expression of KAP-related transcripts but decreased KAP protein expression. In addition, the aberrant splicing generates a dominant negative KAP variant that increases proliferation. We provide the first evidence that KAP not only regulates proliferation but also inhibits migration by decreasing cdc2 mRNA and protein expression. The effect of KAP on cdc2 expression requires its phosphatase activity but does not involve direct dephosphorylation of cdc2. Thus, KAP regulates both cdc2-dependent migration and Cdk2-dependent proliferation, and its loss due to aberrant splicing increases malignancy in human gliomas. [Cancer Res 2007;67(1):130-8]

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“…MS4A3 is a transmembrane protein of the MS4A family expressed in hematopoietic cells and other select cell types and tumors [9]. MS4A3 interacts with the cyclin-dependent kinase 2 (CDK2), cyclin A, and CDK-associated phosphatase complex, and its overexpression in hematopoietic cells has been reported to cause cell cycle arrest at the G0/G1 phase [10]. Thus, MS4A3 can potentially regulate HSC proliferation in vivo.…”

Section: Introductionmentioning

confidence: 99%

Deficiency of GRP94 in the Hematopoietic System Alters Proliferation Regulators in Hematopoietic Stem Cells

Luo

Tseng

Adams

et al. 2013

Stem Cells and Development

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We have previously reported that acute inducible knockout of the endoplasmic reticulum chaperone GRP94 led to an expansion of the hematopoietic stem and progenitor cell pool. Here, we investigated the effectors and mechanisms for this phenomenon. We observed an increase in AKT activation in freshly isolated GRP94-null HSC-enriched Lin -Sca-1 + c-Kit + (LSK) cells, corresponding with higher production of PI(3,4,5)P3, indicative of PI3K activation. Treatment of GRP94-null LSK cells with the AKT inhibitor MK2206 compromised cell expansion, suggesting a causal relationship between elevated AKT activation and increased proliferation in GRP94-null HSCs. Microarray analysis demonstrated a 97% reduction in the expression of the hematopoietic cell cycle regulator Ms4a3 in the GRP94-null LSK cells, and real-time quantitative PCR confirmed this down-regulation in the LSK cells but not in the total bone marrow (BM). A further examination comparing freshly isolated BM LSK cells with spleen LSK cells, as well as BM LSK cells cultured in vitro, revealed specific down-regulation of Ms4a3 in freshly isolated BM GRP94-null LSK cells. On examining cell surface proteins that are known to regulate stem cell proliferation, we observed a reduced expression of cell surface connexin 32 (Cx32) plaques in GRP94-null LSK cells. However, suppression of Cx32 hemichannel activity in wild-type LSK cells through mimetic peptides did not lead to increased LSK cell proliferation in vitro. Two other important cell surface proteins that mediate HSC-niche interactions, specifically Tie2 and CXCR4, were not impaired by Grp94 deletion. Collectively, our study uncovers novel and unique roles of GRP94 in regulating HSC proliferation.

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Binding of HTm4 to Cyclin-dependent Kinase (Cdk)-associated Phosphatase (KAP)·Cdk2·Cyclin A Complex Enhances the Phosphatase Activity of KAP, Dissociates Cyclin A, and Facilitates KAP Dephosphorylation of Cdk2

Cited by 30 publications

References 23 publications

GPR84 sustains aberrant β-catenin signaling in leukemic stem cells for maintenance of MLL leukemogenesis

GPR84 sustains aberrant β-catenin signaling in leukemic stem cells for maintenance of MLL leukemogenesis

Aberrant Splicing of Cyclin-Dependent Kinase–Associated Protein Phosphatase KAP Increases Proliferation and Migration in Glioblastoma

Deficiency of GRP94 in the Hematopoietic System Alters Proliferation Regulators in Hematopoietic Stem Cells

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